Base transceiver stations (BTS) are deployed in wireless telecommunications networks to serve as the interface between mobile subscribers and the network infrastructure facilitating communication capabilities. Each BTS wirelessly transmits information to the subscriber units and also wirelessly receives information from the subscriber units.
BTSs transmit and receive in a generally omni-directional radiation pattern. The area served by this pattern is called a “cell,” with the BTS being located at the center of the cell. This is shown in FIG. 1, where a cell 101 is served by BTS 108. By providing adjacent cells 102-107, each with its own respective BTS, 110-115, mobile subscriber devices 116a-n can move freely from one cell to another. As the subscriber devices 116a-n move from one cell, i.e., geographic area, to another, the system provides a mechanism for switching control of the subscriber devices 116a-n from one BTS to another. More specifically, a subscriber device 116 is handled by a particular BTS when the subscriber device 116 is within the geographic region serviced by the BTS and then handed over to a neighbor BTS as the subscriber unit moves to the neighbor BTS's cell, all without dropping an active call.
The term “backhauling,” as used in a telecommunications context, is used to describe the process of transporting traffic between a BTS and the rest of the network 120, such as, for example, to communicate traffic to the internet. In most wireless systems in use today, each BTS has a wired connection to the rest of the network 120. However, there still remain many BTSs without a hard connection. These BTSs must perform backhauling by wirelessly transmitting information to neighbor BTSs, who either send the information to the core network 120 or must transmit the information to further neighbors if they themselves also do not have hard connections to the rest of the network.
As can be seen in FIG. 1, a BTS 108 serves a cell 101, with a maximum transmission range R, which is the radius of the cell 101. All subscriber units 116a-n will receive coverage from BTS 108 inside of this cell 101. To facilitate transmission to the subscriber units 116a-n within the cell 101 and to other BTS's for backhauling, each BTS is equipped with a power amplifier (PA) 118. If the power required to transmit a signal a distance R is equal to P1, it then follows that a transmission power of at least 4×P1 (+6 dB) is required for a BTS 108 to transmit a distance N=2R to a neighbor BTS 114 for backhauling. This requires a larger power size PA 118 for backhauling transmission compared with the regular access transmission within the cell. As the backhaul direction is not moving, one obvious solution is to replace the backhaul antenna with a high directivity antenna, which can provide higher antenna gain of 18 dB or even more, and may reach higher range of distance. However, those antennas are very expensive, and the higher the directivity the higher the size and the weight and the cost.
It is impractical to install two PAs, one for inter-cell transmissions and a separate, higher-powered PA for backhauling into each BTS. It is also inefficient to install a PA with higher power than is needed to serve a particular cell. Generally speaking, the higher the power rating, the more expensive a PA is to purchase and use. Additionally, once the BTS is given a wired link into the network, and wireless backhauling in no longer necessary, the PA will be at least twice the needed power rating.
Therefore a need exists to overcome the problems with the prior art as discussed above.